Notes on Genus: Ampelovirus

flexuous filaments
flexuous filaments

Type member: Grapevine leafroll-associated virus 3


General Description

This is one of three genera in the family Closteroviridae, which are characterised by their very long (950-2000 nm) and very flexuous particles. Viruses in this genus were previously classified in the genus Closterovirus, but have been separated because of their mealybug transmission and different genome organisation. The name is from the Greek ampelos meaning grapevine, the plant host of the type member.


Virions filamentous, not enveloped, very flexuous, 950-2000 nm long and 10-13 nm in diameter. There is a distinct virion tail. Symmetry helical, with pitch of 3.4-3.7 nm.

Virions composed of 5% nucleic acid.


Monopartite, linear, single-stranded, positive sense RNA 15,000 to 20,000 nucleotides long. There are sequences with potential hairpin structure near the 3'-end. 3' terminus has no poly(A) tract and the 5' terminus probably has a methylated nucleotide cap.

Genus Genomic Organization

The RNA is translated from up to 12 reading frames. There is a large replicase near the 5'-end and the coat proteins are towards (but not at) the 3'-end.

Type Member Genomic Organization

The RNA is believed to be translated from twelve open reading frames:

1a  245 kDa replication protein
1b  61 kDa polymerase, expressed as a 1a/1b fusion protein
2 6 kDa unknown protein
3 5 kDa unknown protein
4 59 kDa similar to the HSP70 heat-shock proteins which are molecular chaperones
5 55 kDa probably involved in cell-to-cell movement
6 35 kDa Coat protein; assembled into particles as the major virion protein
7 53 kDa Minor coat protein incorporated into the virion tail
8 21 kDa unknown protein
9 20 kDa unknown protein
10 20 kDa unknown protein
11 4 kDa unknown protein
12 7 kDa unknown protein